1. Field of the Invention
The present invention is generally concerned with torsional damper devices comprising two coaxial parts disposed to rotate relative to one another within defined limits of relative angular movement against elastic means hereinafter referred to as circumferentially acting elastic means.
2. Description of the Prior Art
This type of torsional damper is normally incorporated in the design of a friction clutch, particularly for automotive vehicles, in which case one coaxial part carries a friction disk designed to rotate with a first shaft, in practice a driving shaft and the motor output shaft in the case of an automotive vehicle, whereas the other of said coaxial parts is carried on a hub designed to rotate with a second shaft, in practice a driven shaft, and the gearbox input shaft in the case of an automotive vehicle.
This type of torsional damper is used to permit regulated transmission of rotational torque applied to one of its coaxial parts where the other is itself subject to a rotational torque. It is thereby able to filter vibrations which may arise at any point in the kinematic system in which it is incorporated, extending from the motor to the driven road wheels in the case of an automotive vehicle.
The present invention is particularly directed towards the case where one of the two coaxial parts concerned comprises a transversely disposed annular flange and the other comprises at least one transversely disposed guide ring, the associated circumferentially acting elastic means comprising individual elastic members each of which is disposed in a housing formed partly by a hole formed for this purpose in said flange and partly by a hole also formed for this purpose in said guide ring.
More often than not, two guide rings are provided, one on each side of the flange and fastened together.
More often than not, the elastic means bear directly in the circumferential direction on the corresponding radial edge of the holes in the guide rings in which they are disposed, these holes also having more or less extensive members along at least one of their circumferential edges adapted to retain elastic members of this kind.
It has already been proposed, in particular in French Pat. No. 740 783, to dispose in the circumferential direction between each of the elastic members and the edge of the hole in the guide ring in which the elastic member is disposed a chock adapted to retain the elastic member when the holes in the guide rings have no such member.
Be this as it may, a general problem to be overcome in producing torsional damper devices of this type is to ensure optimum standardization of their component parts, whatever their specific application conditions, in order to minimize their cost.
From this point of view, it is of benefit to have guide rings adapted to suit various applications in spite of having the same holes for housing elastic members.
For example, in the case of fitting out an automotive vehicle offered to customers in two versions, a standard version and a version with a turbocharger, it is necessary for the torsional damper device used in the second case to have a higher torque rating.
Starting with a torsional damper device which, for the standard version, comprises elastic members constituting the circumferentially acting elastic means and all disposed in holes in the flange and the guide rings and divided into a number of separate groups of elastic members of different stiffness, consideration might be given to replacing the least stiff of these elastic members with elastically deformable arms superposed axially on the coaxial parts concerned and acting circumferentially between them, as described in French Patent Application No. 80 23447 of Nov. 3, 1980 published under the No. 24 93446. For the version with turbocharger, elastic members of higher stiffness would be disposed in the holes thus made available, and adapted to function during the final phase of relative angular movement between said coaxial parts.
However, it is then necessary, and this conflicts with the requirement for standardization, either to decrease the circumferential amplitude of the corresponding holes in the guide rings or to increase that of the corresponding holes in the flange.
Similarly, in the case where at least some of the elastic members utilized are coil springs, it could be beneficial, beginning with guide rings having a given disposition of holes, to be able to reduce artifically the circumferential amplitude of certain at least of these holes so as to accommodate springs shorter than those for which the holes were initially designed, whilst retaining the possibility for less stiff elastic members to function before the latter.
A general object of the present invention is to provide an arrangement with which this objective can be achieved, whilst satisfying the requirement for standardization.